Projection domes



July 14, 1959 K R6SCHKE I 2,894,520

I PROJECTION DOMES Filed Aug. 1; 1956 lnven zar:

United States Patent PROJECTION DOMES Karl Roschke, Jena, Germany, assignor to VEB Carl Zeiss Jena, Jena, Germany Application August 1, 1956, Serial No. 601,853 Claims priority, application Germany January 12, 1956 3 Claims. (Cl. 1354) The invention relates to a projection dome of flexible material for planetaria, which is notable for its simplicity and the ease with which it can be erected and dismantled for frequent transport.

Projection domes for planetaria have been suggested which consists of a folding sheet of canvas suspended in numerous points and inflated by air pressure to form a projection surface, the viewers being admitted through an air lock. Such domes have the disadvantage that they must be perfectly air-tight and that a pressurizer, air conditioning plant and appropriate control equipment are required. A further disadvantage lies in the inconvenience of having to pass visitors in and out of the air lock.

With a projection dome made of flexible material these disadvantages can be eliminated by using an annular supporting unit, preferably consisting of several parts, to which a number of resilient rods guided through suitable runners are attached at one end, the other end being secured preferably to a plate so that when the rods are flexed the projection surface is stretched into the shape of a hemispherical dome.

If the weight of the plate is so calculated as to cause the individual rods to flex as a result of the load applied by the said plate, the projection surface will automatically assume hemispherical shape.

The dome can be very easily assembled if the rods are secured to the plate by means of joints.

An embodiment of the invention is shown in the drawing, the individual figures relating to the following items:

Fig. 1.-The projection dome in side elevation.

Fig. 2.-Part section through the dome, larger scale.

Fig. 3.Arr-angement of seams between fabric webs.

Fig. 4.-Method of inserting rods, and

"2,894,520 Patented July 14, 1959 "ice Fig. 5.-Articulated attachment of two opposite rods.

The projection surface consists of twenty four canvas webs 1 sewn together by means of twenty four double seams 2 in such a manner that runners 3 are formed between each pair of seams. One rod 4 is pushed through each one of these runners. One end of each rod 4 is articulated to a plate 6 by means of eyelets 5, ends 7 of rods 4 being inserted into bores 8 of the multisectional ring 9. The weight of plate 6instead of which it is also possible to use a ring-causes rods 4 to flex so that the projection surface automatically assumes the shape of a hemispherical dome. This projection dome is mounted on columns 10. The projection head of the planetarium can be easily located in the centre of the hemisphere.

I claim:

1. A projection dome for planetaria comprising an annular supporting means in combination with a foldable projection screen made of flexible material, said foldable projection screen when completely open forming an hemispherical projection dome having an equator about its lower edge and a zenith at the top, said projection dome having on its outer surface a plurality of runners disposed along meridian lines beginning near the zenith and running to the equator of the hemispherical projection dome, nonfoldable straight flexible rods disposed in said runners, said rods having ends which are detachably securable to said annular supporting means at about the equator of said hemispherical projection dome and the other ends of the rods being movably secured to a weighted supporting means at about the zenith of said hemispherical projection dome, said weighted supporting means being sufficiently heavy to flex said rods when said screen is open in viewing position to keep said screen in a hemispherical dome configuration which is main tained by the configuration of the screen.

2. A projection dome according to claim 1 wherein said annular supporting means is multisectional.

3. A device according to claim 1 including columns for supporting said annular ring above the ground.

References Cited in the file of this patent UNITED STATES PATENTS 1,516,372 Brooks Nov. 18, 1924 2,477,027 Wenberg July 26, 1949 2,753,818 Green July 10, 1956 2,755,009 Parker July 17, 1956 

